Cargando…

Loss of Bacteroides thetaiotaomicron bile acid altering enzymes impact bacterial fitness and the global metabolic transcriptome

Bacteroides thetaiotaomicron (B. theta) is a Gram-negative gut bacterium that encodes enzymes that alter the bile acid pool in the gut. Primary bile acids are synthesized by the host liver and are modified by gut bacteria. B. theta encodes two bile salt hydrolases (BSHs), as well as a hydroxysteroid...

Descripción completa

Detalles Bibliográficos
Autores principales: McMillan, Arthur S., Foley, Matthew H., Perkins, Caroline E., Theriot, Casey M.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Cold Spring Harbor Laboratory 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10327073/
https://www.ncbi.nlm.nih.gov/pubmed/37425690
http://dx.doi.org/10.1101/2023.06.27.546749
_version_ 1785069552831299584
author McMillan, Arthur S.
Foley, Matthew H.
Perkins, Caroline E.
Theriot, Casey M.
author_facet McMillan, Arthur S.
Foley, Matthew H.
Perkins, Caroline E.
Theriot, Casey M.
author_sort McMillan, Arthur S.
collection PubMed
description Bacteroides thetaiotaomicron (B. theta) is a Gram-negative gut bacterium that encodes enzymes that alter the bile acid pool in the gut. Primary bile acids are synthesized by the host liver and are modified by gut bacteria. B. theta encodes two bile salt hydrolases (BSHs), as well as a hydroxysteroid dehydrogenase (HSDH). We hypothesize that B. theta modifies the bile acid pool in the gut to provide a fitness advantage for itself. To investigate each gene’s role, different combinations of genes encoding bile acid altering enzymes (bshA, bshB, and hsdhA) were knocked out by allelic exchange, including a triple KO. Bacterial growth and membrane integrity assays were done in the presence and absence of bile acids. To explore if B. theta’s response to nutrient limitation changes due to the presence of bile acid altering enzymes, RNASeq analysis of WT and triple KO strains in the presence and absence of bile acids was done. WT B. theta is more sensitive to deconjugated bile acids (CA, CDCA, and DCA) compared to the triple KO, which also decreased membrane integrity. The presence of bshB is detrimental to growth in conjugated forms of CDCA and DCA. RNA-Seq analysis also showed bile acid exposure impacts multiple metabolic pathways in B. theta, but DCA significantly increases expression of many genes in carbohydrate metabolism, specifically those in polysaccharide utilization loci or PULs, in nutrient limited conditions. This study suggests that bile acids B. theta encounters in the gut may signal the bacteria to increase or decrease its utilization of carbohydrates. Further study looking at the interactions between bacteria, bile acids, and the host may inform rationally designed probiotics and diets to ameliorate inflammation and disease. IMPORTANCE: Recent work on BSHs in Gram-negative bacteria, such as Bacteroides, has primarily focused on how they can impact host physiology. However, the benefits bile acid metabolism confers to the bacterium that performs it is not well understood. In this study we set out to define if and how B. theta uses its BSHs and HSDH to modify bile acids to provide a fitness advantage for itself in vitro and in vivo. Genes encoding bile acid altering enzymes were able to impact how B. theta responds to nutrient limitation in the presence of bile acids, specifically carbohydrate metabolism, affecting many polysaccharide utilization loci (PULs). This suggests that B. theta may be able to shift its metabolism, specifically its ability to target different complex glycans including host mucin, when it comes into contact with specific bile acids in the gut. This work will aid in our understanding of how to rationally manipulate the bile acid pool and the microbiota to exploit carbohydrate metabolism in the context of inflammation and other GI diseases.
format Online
Article
Text
id pubmed-10327073
institution National Center for Biotechnology Information
language English
publishDate 2023
publisher Cold Spring Harbor Laboratory
record_format MEDLINE/PubMed
spelling pubmed-103270732023-07-08 Loss of Bacteroides thetaiotaomicron bile acid altering enzymes impact bacterial fitness and the global metabolic transcriptome McMillan, Arthur S. Foley, Matthew H. Perkins, Caroline E. Theriot, Casey M. bioRxiv Article Bacteroides thetaiotaomicron (B. theta) is a Gram-negative gut bacterium that encodes enzymes that alter the bile acid pool in the gut. Primary bile acids are synthesized by the host liver and are modified by gut bacteria. B. theta encodes two bile salt hydrolases (BSHs), as well as a hydroxysteroid dehydrogenase (HSDH). We hypothesize that B. theta modifies the bile acid pool in the gut to provide a fitness advantage for itself. To investigate each gene’s role, different combinations of genes encoding bile acid altering enzymes (bshA, bshB, and hsdhA) were knocked out by allelic exchange, including a triple KO. Bacterial growth and membrane integrity assays were done in the presence and absence of bile acids. To explore if B. theta’s response to nutrient limitation changes due to the presence of bile acid altering enzymes, RNASeq analysis of WT and triple KO strains in the presence and absence of bile acids was done. WT B. theta is more sensitive to deconjugated bile acids (CA, CDCA, and DCA) compared to the triple KO, which also decreased membrane integrity. The presence of bshB is detrimental to growth in conjugated forms of CDCA and DCA. RNA-Seq analysis also showed bile acid exposure impacts multiple metabolic pathways in B. theta, but DCA significantly increases expression of many genes in carbohydrate metabolism, specifically those in polysaccharide utilization loci or PULs, in nutrient limited conditions. This study suggests that bile acids B. theta encounters in the gut may signal the bacteria to increase or decrease its utilization of carbohydrates. Further study looking at the interactions between bacteria, bile acids, and the host may inform rationally designed probiotics and diets to ameliorate inflammation and disease. IMPORTANCE: Recent work on BSHs in Gram-negative bacteria, such as Bacteroides, has primarily focused on how they can impact host physiology. However, the benefits bile acid metabolism confers to the bacterium that performs it is not well understood. In this study we set out to define if and how B. theta uses its BSHs and HSDH to modify bile acids to provide a fitness advantage for itself in vitro and in vivo. Genes encoding bile acid altering enzymes were able to impact how B. theta responds to nutrient limitation in the presence of bile acids, specifically carbohydrate metabolism, affecting many polysaccharide utilization loci (PULs). This suggests that B. theta may be able to shift its metabolism, specifically its ability to target different complex glycans including host mucin, when it comes into contact with specific bile acids in the gut. This work will aid in our understanding of how to rationally manipulate the bile acid pool and the microbiota to exploit carbohydrate metabolism in the context of inflammation and other GI diseases. Cold Spring Harbor Laboratory 2023-06-27 /pmc/articles/PMC10327073/ /pubmed/37425690 http://dx.doi.org/10.1101/2023.06.27.546749 Text en https://creativecommons.org/licenses/by-nc-nd/4.0/This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (https://creativecommons.org/licenses/by-nc-nd/4.0/) , which allows reusers to copy and distribute the material in any medium or format in unadapted form only, for noncommercial purposes only, and only so long as attribution is given to the creator.
spellingShingle Article
McMillan, Arthur S.
Foley, Matthew H.
Perkins, Caroline E.
Theriot, Casey M.
Loss of Bacteroides thetaiotaomicron bile acid altering enzymes impact bacterial fitness and the global metabolic transcriptome
title Loss of Bacteroides thetaiotaomicron bile acid altering enzymes impact bacterial fitness and the global metabolic transcriptome
title_full Loss of Bacteroides thetaiotaomicron bile acid altering enzymes impact bacterial fitness and the global metabolic transcriptome
title_fullStr Loss of Bacteroides thetaiotaomicron bile acid altering enzymes impact bacterial fitness and the global metabolic transcriptome
title_full_unstemmed Loss of Bacteroides thetaiotaomicron bile acid altering enzymes impact bacterial fitness and the global metabolic transcriptome
title_short Loss of Bacteroides thetaiotaomicron bile acid altering enzymes impact bacterial fitness and the global metabolic transcriptome
title_sort loss of bacteroides thetaiotaomicron bile acid altering enzymes impact bacterial fitness and the global metabolic transcriptome
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10327073/
https://www.ncbi.nlm.nih.gov/pubmed/37425690
http://dx.doi.org/10.1101/2023.06.27.546749
work_keys_str_mv AT mcmillanarthurs lossofbacteroidesthetaiotaomicronbileacidalteringenzymesimpactbacterialfitnessandtheglobalmetabolictranscriptome
AT foleymatthewh lossofbacteroidesthetaiotaomicronbileacidalteringenzymesimpactbacterialfitnessandtheglobalmetabolictranscriptome
AT perkinscarolinee lossofbacteroidesthetaiotaomicronbileacidalteringenzymesimpactbacterialfitnessandtheglobalmetabolictranscriptome
AT theriotcaseym lossofbacteroidesthetaiotaomicronbileacidalteringenzymesimpactbacterialfitnessandtheglobalmetabolictranscriptome